Hydrofest 2016

The Hydrographic Society in Scotland

HYDROFEST 2016

The Hydrographic Society in Scotland

POSITIONING SYSTEMS Karel Zuidweg

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HYDROFEST 2016

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1. GNSS Positioning 2. Heading and Motion Sensors 3. Navigation Software 4. Relative Positioning 5. Inertial Navigation Systems (INS)

GNSS = GPS + Glonass + Galileo + Beidou

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SBAS: Space Based Augmentation Service (Free) PPP: Precise Point Positioning (Commercial Augmentation Service) IAR: Integer Ambiguity Resolution (Commercial Augmentation Service)

SBAS (e.g. EGNOS) <6 m

GNSS ~30 m

Differential 2 - 4 m

PPP or IAR 6 - 20 cm

1. GNSS Positioning

95% Confidence (2σ):

GNSS Horizontal Accuracies

Main Error Sources: Ionosphere Troposphere Satellite Clock Satellite Orbit Receiver Noise Multipath Geophysical Effects

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Offshore Correction Service

Correction Type Horizontal Accuracy (95%)

Satellites

CNav C1 PPP 10 cm GPS

CNav C2 PPP 8 cm GPS, Glonass

Fugro Starfix G4, PPP 10 cm GPS, Glonass, Galileo, Beidou,

Fugro Starfix G2, XP2 PPP 10 cm GPS, Glonass

Fugro Starfix HP IAR 10 cm GPS

Fugro Starfix G2+ PPP + IAR 3 cm GPS, Glonass

Veripos Std2 DGNSS 1 m GPS, Glonass

Veripos Ultra2 PPP 10 cm GPS, Glonass

Veripos Apex2 PPP 5 cm GPS, Glonass

Others: Positioneering, Atlas, Various Land Services

1. GNSS Positioning

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GNSS Practical Considerations

Antenna Placement

Cable Run

QC Software

1. GNSS Positioning

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GNSS alone is not enough

GNSS Antenna E, N

Grid North

Additional to GNSS you need: - Offsets measured by tape measure or total station

- Heading - Usually also Pitch, Roll and Heave

1. GNSS Positioning

Vertical

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Technology Accuracy 2σ Examples Remarks

Spinning Mass

Gyro

Gimballed spinning

gyroscope

0.2° static *

0.4° dynamic

TSS Meridian

Surveyor

Fibre Optic

Gyro

Laser interferometer

measuring Sagnac effect in

a fibre coil

0.2° * IXSEA Octans, CDL

TOGS

Also does Pitch,

Roll, Heave

Ring Laser

Gyro

Laser resonance in a

clockwise and anticlockwise

beam

0.3°-0.1° * CDL Mini RLG,

Sonardyne Lodestar,

Kearfott T16, T24

Also does Pitch,

Roll, Heave

Hemispherical

Resonator

Flexural resonance of dome

moves with rotation

0.2° * Sagem BlueNaute Also does Pitch,

Roll, Heave

GNSS Vector

Heading

Relative GNSS positioning 0.6° ** Hemisphere V series

GNSS RTK

heading

Carrier Phase count

between base and rover

0.1° ** Trimble SPS361,

Fugro, Cnav, Veripos

* Depends on latitude ** Depends on baseline length

Heading Sensors

2. Heading and Motion Sensors

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Heading Sensors Practical Considerations

Alongside - Dual antenna GNSS RTK heading - Land surveying vessel bow and stern - Tape measurement to known

quayside heading

Offshore - Dual antenna GNSS RTK heading - Sextant measurement to known points

e.g. platforms - Sunshot

Aligning the gyro with the local Y-axis (usually the vessel longitudinal axis)

2. Heading and Motion Sensors

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Motion Sensors (Pitch, Roll, Heave)

“AHRS” Attitude & Heading Reference System (~0.02° / 5 cm 2σ)

MEMS Pitch, Roll, Heave Sensors (~0.1° / 10 cm 2σ)

Combined GNSS and IMU Systems

Ixblue Octans Sonardyne Lodestar

TSS DMS-05 SBG Ekinox

Applanix POS-MV Coda Octopus F180

Kongsberg MRU-5

2. Heading and Motion Sensors

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* RMS error secant latitude so divided by cos(60)

2. Heading and Motion Sensors

Putting It All Together: Error Budget

Example at 60° Latitude

Standard Deviation

(deg) Offset

(m)

Standard Deviation

(m) Variance

(m2)

GPS position 0.05 0.003

Offset measurements 0.10 0.010

TSS Gyro Dynamic error 0.40* 50 0.35 0.123

TSS Gyro Settling error 0.20* 50 0.17 0.029

Gyro Cal error 0.20 50 0.17 0.029

Total σ (68% conf) 0.44 0.194

2σ (95% conf) 0.88

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Putting It All Together: Nav Software

Multi Purpose Nav Software: - EIVA NaviPac - QPS Qinsy - Fugro Starfix - Others: Hypack, NavView, legacy software Winfrog, Hydropro, etc

GNSS (PPP) Heading

Pitch/Roll/Heave

• Geodetic Parameters • X, Y, Z Offsets • Calibrations (C-O) • Vessel Graphics • Background Files • Planning Lines/Points .. And Other Sensors

3. Nav Software

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Relative Positioning

Applications: - Rig Positioning alongside a Platform - Platform Installation - Seismic Streamer Tailbuoy Positioning - Dynamic Positioned vessel close to

platform

Methods: - Total Station - Moving Base GNSS RTK - Fanbeam, Radascan

4. Relative Positioning

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Inertial Navigation System (INS)

5. Inertial Nav Systems

Add good quality accelerometers to an AHRS and you can do Inertial Navigation (dead reckoning).

Problem: INS Drifts

Underwater options: - Zero Velocity Update “ZUPT” - Doppler Velocity - USBL Aiding - Acoustic Ranges (SLAM, Sparse Array)

Surface Options: - GNSS Aiding

Drift Mitigation

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Multibeam Stabilisation

INS Application Examples

ROV/AUV Positioning

GNSS Aiding

Typically used to smooth positioning, increase update rates, reduce spikes, or fill-in during acoustic outages.

Doppler Velocity Log, Depth Sensor, LBL/USBL Aiding, SLAM, Pattern Recognition etc.

Zero Velocity Update, SLAM

Subsea Metrology